This invention relates to para-ordered aromatic heterocyclic copolymers. In particular, this invention relates to crosslinkable, para-ordered aromatic heterocyclic copolymers.
Para-ordered, rigid-rod aromatic heterocyclic polymers, such as poly(p-phenylenebenzobisthiazole) (PBT) and poly(p-phenylenebenzobisoxazole) (PBO) are well known for their outstanding thermal, physical and chemical properties. These polymers exhibit lyotropic behavior in strongly acidic solvents, such as methanesulfonic acid (MSA) or polyphosphoric acid (PPA) and can be readily spun into fibers or made into films which have exceptional tensile strength and modulus. The high thermooxidative stability of these fibers and films, together with their exceptional tensile properties and electrical non-conductivity make them obvious candidates as a reinforcement in advanced composite materials. However, a serious obstacle to the successful use of PBT or PBO fibers in high temperature composites is their relatively low compressive strength. Tsai et al, U.S. Pat. No. 4,835,246, disclose para-ordered, rigid-rod aromatic heterocyclic polymers having pendant benzazole groups, which exhibit increased compressive strength. We have sought to increase compressive strength through crosslinking of the polymers.
Accordingly, it is an object of the present invention to provide novel para-ordered, rigid-rod aromatic heterocyclic polymers having increased compressive strength.
Other objects, aspects and advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the invention.